Dams in South Africa’s Cape Town are half of what they were this time last year as the city continues to battle drought. Last year’s shortage gave the city the driest summer in 100 years. Unless Cape Town has a miraculously wet spring, the summer of 2018 seems set to achieve some unfortunate new records.

Slowing down residential water use is obviously hugely important – residents consume 65 percent of the city’s water. But to get residents to use less, the city’s management must get residents’ buy-in. This can only be achieved if there is trust and trust will only be developed when residents believe that the water authority is handling restrictions in a way that is necessary, effective and fair.

Australian researchers studying household water use found that people’s willingness to save water relates directly to the trust they feel in the local authority promoting water savings. The researchers also drew on a Mexican case study which found that residents who trusted the local authority in a town called Sonora during an eight-year drought were much more likely to save water.

Necessary: people must believe that the appropriate restrictions have been introduced at the correct time.

Queensland, Australia, for example, ran a campaign called “Target 140” during their worst drought in 100 years. The aim of the campaign was to reduce water use to 140 litres per person per day. One of the greatest hindrances was that people had already endured two years of water restrictions. So they felt despondent that their best water saving efforts hadn’t been good enough and were reluctant to save even more.

But the campaign became a success after the Queensland water commission began showing residents how dam levels were dropping. It was able to convince customers that intensified water restrictions were absolutely necessary.

Effective: Residents can lose interest in conserving water if they believe that others are getting away with wasting water. A study on water restriction effectiveness in Los Angeles found that hardly any water was saved as long as water restrictions were not enforced. People need to know that water restrictions are going to be effective.

Fair: Customers must trust that restrictions are applied appropriately to all water users. Case studies show that one of the most common complaints by residents is that others – particular groups or other residents – are the real water wasters. Queensland’s Target 140 Campaign managed to convince customers that severe restrictions on the residential sector, which used 70 percent of the water, were fair. Reassuring residents of the fairness of restrictions is vital to sustain buy-in.

Is Cape Town building trust?

The City of Cape Town has done a good job in covering the bases when it comes to explaining water restrictions in terms of their necessity and their effectiveness. But it hasn’t done that well in explaining that water restrictions are being done fairly.

On the positive end of the scale, the city has done a good job in demonstrating that those who waste water are held accountable. This has been achieved through the naming and shaming of top water users. And water management devices were installed on private properties that hadn’t curtailed excessive use.

But, on fairness, the city has only sporadically communicated the breakdown of water distribution from the 14 dams that supply its water, it’s rarely shown the breakdown of water use per sector and scant mention has been made of restrictions placed on other sectors.

What can the city do differently?

Cape Town is emulating some of the best elements of a save-water campaign. Cape Town’s water saving target is close on half of Queensland’s, which was considered one of the most water-efficient communities in the western world.

If Cape Town wants to beat Queensland’s target, it needs to spend the spring season convincing the public that restrictions are applied appropriately for all water users.

This means changing tack in its messaging. Up until now the dominant message has been aimed at convincing the public that restrictions are necessary and effective. Now it’s time to show that restrictions are fair.

This means showing exactly how water is allocated in the region, breaking down the distribution of water to various sectors and demonstrating that nonresidential sectors are also carrying their responsibility. This information is already in the public domain, but it needs greater emphasis.

A chain is as strong as its weakest link. Building trust, and getting the public to buy in to severely reduced water use over 2018, will be best achieved if the city can communicate the fairness of restrictions to fortify an otherwise robust campaign.